Fuel cells provide electrical power by converting a source fuel, such as hydrogen or a hydrogen-containing compound, into an electric current and a waste product by electrochemical means. In particular, a fuel cell contains an anode, a cathode, and an electrolyte between the anode and cathode. Electricity may be generated by two chemical reactions within the fuel cell. First, a catalyst at the anode oxidizes the fuel to produce positively charged ions and electrons. The electrolyte may allow ions from the oxidation process to pass through to the cathode while blocking passage of the electrons. The electrons may thus be used to drive a load connected to the fuel cell before recombining with the ions and a negatively charged atom (e.g., oxygen) at the cathode to form a waste product such as carbon dioxide and/or water.
Because fuel cells are typically associated with low voltages (e.g., 0.5-0.7 volts), multiple fuel cells may be combined to form a fuel cell stack. For example, a fuel cell stack may contain a number of stacked bipolar plates. Each bipolar plate may provide an anode on one side and a cathode on the other side. To form fuel cells within the stack, the catalyst and the electrolyte may be placed in between the bipolar plates. The fuel cells may then be connected in series to increase the voltage of the fuel cell stack.
However, existing fuel cell stack architectures may have a number of disadvantages. First, each fuel cell may represent a single point of failure in a series-connected fuel cell stack. In addition, a fuel cell may be subject to a number of failure modes, including accumulation of nitrogen in the anode, poisoning of the catalyst, degradation of the electrolyte, and/or water flooding in the anode or cathode. Consequently, the reliability of a fuel cell stack may decrease as the number of fuel cells in the fuel cell stack increases.
Second, bipolar plates for fuel cell stacks are typically manufactured using materials that are both conductive and corrosion-resistant, such as stainless steel. However, the high density of such materials may result in heavy bipolar plates that restrict the use of fuel cell stacks in portable applications. For example, adoption of a fuel cell stack design as a power source for portable electronic devices may be hampered by the weight of the resulting fuel cell stack, the majority of which is in stainless steel bipolar plates.
Hence, the use of fuel cells as power sources may be facilitated by improvements in the reliability, weight, and/or size of fuel cell stacks.